The present disclosure relates to a light ray direction controlling device and a display device.
With display devices being smaller, lighter, and more highly-defined and the widespread of wireless network that enables users to connect to information from anywhere, it has become possible to process various types of information via smartphones, tablets, or laptop computers regardless of time and place. However, although being able to handle various types of information from anywhere makes people's life more convenient, accessing information in places where the users are surrounded by many other people such as restaurants, parks, or trains and buses creates the risk of information leak.
To solve this problem, a viewing angle controlling film has been used. The viewing angle controlling film is configured to absorb light that is output toward the diagonal direction so that the screen can be viewed only from the front side, thereby mitigating the risk of information leak. However, when this film is used, the viewing angle is constantly narrow, and therefore, in order to perform another task that requires a display with wide viewing angle, the viewing angle controlling film needs to be physically removed.
As opposed to a louver with a fixed viewing angle that needs to be removed physically, a means to switch between the wide viewing angle mode and the narrow viewing angle mode by electrical control has been developed. For example, Japanese Patent Application Laid-open Publication No. 2013-50740 discloses a configuration where a louver with a fixed viewing angle and an element that can switch between the light scattering state and transparent state electrically, such as a PDLC (polymer dispersed liquid crystal), are stacked.
Japanese Patent Application Laid-open Publication No. 2016-62092 discloses an active louver that includes electrophoretic elements. The active louver switches between the light absorption state and transparent state by changing the driving voltage of the electrophoretic element. This makes it possible for the display device to switch between the narrow viewing angle mode and the wide viewing angle mode. Japanese Patent Application Laid-open Publication No. 2007-206373 discloses an active louver that uses PDLC. By switching between the light scattering state and the transparent state of the PDLC, the display device can switch between the narrow viewing angle mode and the wide viewing angle mode.